Folks all across the northern hemisphere have noticed pronounced changes in climate patterns this year. The US Mid-West had an unusually brutal winter that seems to have stuck around far longer than usual, while UK and parts of Europe experienced unseasonal bad stormy weather.
The weather is probably best explained by the unusual pattern of winds circling the earth several thousands of feet above sea-level. Researchers at University of Rutgers, New Jersey suggest that a shifting jet stream, that is now increasingly taking a longer, meandering path is to blame for the recent woes.
What Is Jet Stream?
Did you know that the earth’s atmosphere is made of several layers? About 30,000 feet above the surface of the earth is an area that is home to a narrow zone of high-speed winds that can travel at 200 miles per hour. This ribbon of wind is the jet stream and it can extend several thousands of miles long.
Jet streams form because of a combination of the rotation of the earth and the presence of significant temperature differences between air masses. Jet streams create a strong influence on global weather patterns and meteorologists closely track their position to help forecast weather.
Jet streams flow in both the northern and southern hemispheres. The polar jet streams are strong and tend to circulate between 23000 and 39000 feet above sea level. Subtropical jet streams tend to be weaker and usually flow between 33000 and 52000 ft above sea level. The northern polar jet meanders over the middle to northern latitudes of North America, Europe and Asia from the west to the east.
A Wavier Ribbon
Have you noticed how fast flowing rivers tend to cut a straight path, while slow-moving rivers tend to meander along? When temperature differences between the Arctic and the mid-latitudes are large, the jet stream speeds up and like a river flowing down a steep hill, it ploughs through obstacles - such as areas of high pressure, that might be in its way.
However, when temperature differences reduce because of a warming Arctic, the jet stream weakens and like a river in a flat bed, it meanders and flows around, every time it comes across an obstacle. With no pressure to keep the jet stream moving quickly, weather patterns tend to hang around and remain stuck for weeks on end.
With weaker jet streams, the otherwise slight wavy flow of wind patterns is replaced by a pattern that has distinct troughs and crests. This explains the deep freeze in places like Atlanta brought on by a sharper trough in the jet stream that sent cold air further south, as well as the unusually warm winter in Alaska and parts of Scandinavia because of higher crest in the jet stream.